Magnetic sensor and method of fabricating the same

ABSTRACT

Provided are a magnetic sensor and a method of fabricating the same. The magnetic sensor includes: hall elements disposed in a substrate, a protection layer disposed on the substrate, a seed layer disposed on the protection layer, and an integrated magnetic concentrator (IMC) formed on the seed layer, the seed layer and the IMC each having an uneven surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.13/951,093 filed on Jul. 25, 2013, now U.S. Pat. No. 9,419,206 issued onAug. 16 2016, which claims the benefit under 35 USC 119(a) of KoreanPatent Application No. 10-2013-0025230 filed on Mar. 8, 2013, in theKorean Intellectual Property Office, the entire disclosures of which areincorporated herein by reference for all purposes.

BACKGROUND

1. Field

The following description relates to a magnetic sensor and a method offabricating the same, and to a magnetic sensor including hall elementsand an integrated magnetic concentrator (IMC) that may detect adirection of a magnetic field and a method of fabricating the same.

2. Description of Related Art

A magnetic sensor is used to detect a magnetic field. A magnetic sensorthat combines a hall element and an integrated magnetic concentrator(IMC) may be used to detect a direction of a magnetic field.

In an example of such a magnetic sensor, an IMC is formed of a magneticmaterial with a flat shape. A hall-effect device is disposed in an edgeportion of the IMC of the magnetic sensor. Such a magnetic senor may beused to detect a direction of a three-dimensional magnetic field.

The magnetic sensor having the configuration is effective in detecting ahorizontal magnetic field and amplifying a magnetic field in a region inwhich the hall-effect device is disposed through the IMC.

FIG. 1 is a plan view illustrating a magnetic sensor disclosed in U.S.Pat. No. 6,545,462. The reference numeral 3 denotes an IMC, and thereference numerals 2.1 to 2.6 denote hall-effect elements.

The magnetic sensor having the configuration as illustrated in FIG. 1includes an IMC 3 having a flat upper surface and a flat lower surface.The flat shape of the IMC 3 results in high stress to the hall-effectelements 2.1 to 2.6 and causes an offset voltage of the magnetic sensorto increase. Therefore, it is desirable to reduce the stress and tolower the offset voltage of such a magnetic sensor.

In the magnetic sensor of FIG. 1, a voltage of the hall-effect elementhas to be zero (0) when a magnetic field is not applied. However, thevoltage of the hall-effect element may have values other than zero (0).The offset voltage denotes a voltage difference when the voltage of thehall-effect element has values other than zero (0). As the offsetvoltage increases, malfunction is more likely to occur in the magneticsensor. Further, when a magnetic field is applied to a device having alarge offset voltage, the change in the voltage of the hall-effectelement is insignificant and the sensitivity of the device is reduced.In other words, a ratio of signal to noise is reduced because the offsetvoltage is large. In applications in which fine changes in magneticfield are detected, it is difficult to detect the fine changes with amagnetic sensor having a high offset voltage.

SUMMARY

In one general aspect, there is provided a magnetic sensor including:hall elements disposed in a substrate; a protection layer disposed onthe substrate; a seed layer disposed on the protection layer; and anintegrated magnetic concentrator (IMC) formed on the seed layer, theseed layer and the IMC each having an uneven surface.

An area of the IMC may be equal to or larger than an area of the seedlayer.

The protection layer may include a plurality of protrusions formed on asurface thereof.

The uneven surface of the seed layer and the uneven surface of the IMCmay each have a cross-section in which a plurality of concave portionsand a plurality of convex portions are arranged.

One of the hall elements may overlap with an edge portion of the IMC ina vertical direction.

The protection layer may include a passivation insulating layer and abuffer layer.

The protection layer may further include a corrosion barrier layer.

The corrosion barrier layer may include a silicon oxide layer or asilicon nitride layer.

The corrosion barrier layer may have a thickness of 5 to 50 nm.

The corrosion barrier layer may be interposed between the passivationinsulating layer and the buffer layer.

The protrusions may include polyimide.

The IMC may include a nickel-iron (NiFe) alloy, and an iron content ofthe nickel-iron alloy may be in a range of 10 to 30 atomic %.

The seed layer may include a titanium tungsten (TiW) layer and a copper(Cu) layer.

In another general aspect, there is provided a method of fabricating amagnetic sensor, the method involving: forming a protection layer on asubstrate in which a plurality of hall elements are disposed; forming abuffer layer on the protection layer; forming a plurality of protrusionson a surface of the buffer layer; forming a seed layer having an unevensurface corresponding to the plurality of protrusions; and forming anintegrated magnetic concentrator (IMC) having an uneven surface on theseed layer.

The uneven surface of the seed layer or the uneven surface of the IMCmay have a cross-section in which a plurality of concave portions and aplurality of convex portions are arranged.

The seed layer may include a titanium tungsten (TiW) layer and a copper(Cu) layer.

The general aspect of the method may further involve forming a corrosionbarrier layer.

The corrosion barrier layer may include a silicon oxide layer or asilicon nitride layer.

The corrosion barrier layer may be formed between the protection layerand the buffer layer.

The protrusions may include polyimide.

In another general aspect, there is provided a magnetic sensorincluding: hall elements; and an integrated magnetic concentrator (IMC)disposed above the hall elements, the IMC having an uneven surface, andthe plurality hall elements being disposed below the IMC such that anedge portion of the IMC overlaps with a width of the hall elements in avertical direction.

The uneven surface of the IMC may include an elevated portion in a shapeof one or more concentric rings.

Other features and aspects may be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a magnetic sensor.

FIG. 2A is a cross-sectional view illustrating an example of a magneticsensor.

FIG. 2B is a plan view of the magnetic sensor illustrated in FIG. 2A.

FIGS. 3A to 3N are cross-sectional views illustrating an example of amethod of fabricating a magnetic sensor.

FIGS. 4A to 4O are cross-sectional views illustrating another example ofa method of fabricating a magnetic sensor.

FIGS. 5A and 5B are views illustrating scanning electron microscope(SEM) photographs of an example of an IMC of a magnetic sensorrespectively from the top and a cross-sectional view of the IMC.

FIG. 6A and 6B are graphs illustrating stress in an X-axis direction andstress in a Y-axis direction that affect a hall element of an example ofa magnetic sensor.

FIG. 7A and 7B are a graph illustrating a magnetic flux simulationresult of an example of an IMC.

Throughout the drawings and the detailed description, unless otherwisedescribed, the same drawing reference numerals will be understood torefer to the same elements, features, and structures. The relative sizeand depiction of these elements may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. Accordingly, various changes,modifications, and equivalents of the systems, apparatuses and/ormethods described herein will be suggested to those of ordinary skill inthe art. Also, descriptions of well-known functions and constructionsmay be omitted for increased clarity and conciseness.

It will be understood that, although the terms first, second, A, B, etc.may be used herein in reference to elements of various examples, suchelements should not be construed as to be limited by these terms. Forexample, a first element could be termed a second element, and a secondelement could be termed a first element, without departing from thescope of the present disclosure. Herein, the term “and/or” includes anyand all combinations of one or more referents.

The terminology used herein is for the purpose of describing an exampleonly and is not intended to be limiting of the present disclosure. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Hereinafter, various examples will be described with reference to theaccompanying drawings.

FIG. 2A is a cross-sectional view illustrating an example of a magneticsensor.

Referring to FIG. 2A, the magnetic sensor 200 includes a substrate 220in which a plurality of hall elements 210 are formed. The substrate 220may be a semiconductor substrate. A protection layer 230 is formed onthe substrate 220, and a seed layer 240 is formed on the protectionlayer 230. An integrated magnetic concentrator (IMC) 250 is formed onthe seed layer 240. The seed layer 240 and the IMC 250 each have anuneven surface. The protection layer 230 may include a passivationinsulating layer and a buffer layer. The passivation insulating layercan be formed on the buffer layer, or the buffer layer can be formed onthe passivation insulating layer. The passivation insulating layer mayinclude a silicon oxide layer and a silicon nitride layer. Thepassivation insulating layer may prevent moisture from penetrated into achip. A corrosion barrier layer configured to prevent a pad from beingcorroded may be further formed on the passivation insulating layer. Thecorrosion barrier layer may include a silicon oxide layer. The bufferlayer may include a polymer material such as polyimide.

To form the uneven surface of the seed layer 240, a plurality ofprotrusions (or elevations) 235 a are formed on a surface of theprotection layer 230. A width and height of the protrusions 235 a andthe number of protrusions 235 a are designed to minimize stressaffecting the hall element 210. For example, the width of the protrusion235 a may be in a range of 5 to 30 μm, the height of the protrusion 235a may be in a range of 1 to 10 μm, and the number of protrusions 235 amay be 1 to 8. As the number of protrusions 235 a is increased, thestress affecting the hall element may be minimized Since the protrusions235 a are formed by etching the buffer layer 230, the protrusions areformed of a polymer material such as polyimide.

Each of the IMC 250 and the seed layer 240 may have a circular shape ora polygonal shape in a plan view.

To increase sensibility of the hall element 210 to a magnetic field, thehall element 210 is disposed so that a portion of the hall element 210overlaps with an edge portion B of the IMC 250 in the vertical directionof the magnetic sensor 200. Referring to FIG. 2A, the hall element 210may have a width A, and the edge portion B of the IMC 250 may overlapwith the width A in the vertical direction. For example, the width ofthe hall element 210 may be equal to or less than 50 μm. The hallelement 210 may be disposed so that a center portion of the hall element210 overlaps with an edge portion B of the IMC 250, the center portionof the hall element 210 being disposed within the width A of the hallelement 210. In an example in which the hall element 210 has a width ofapproximately 50 μm, the edge portion B of the IMC 250 may overlap witha center portion of the hall element 210 approximately 25 μm from theedge of the hall element 210, for example.

A distance C from a top of the hall element 210 to a bottom of the IMC250 may be, for example, in a range of 1 to 30 μm.

The IMC 250 may be formed of a magnetic material, and the magneticmaterial may be formed using electroplating.

The magnetic material may include an alloy containing two or morecomponents selected from the group consisting of nickel (Ni), iron (Fe),cobalt (Co), and manganese (Mn). The magnetic material may have acoefficient of thermal expansion in a range of 5 to 20 ppm/° C. When themagnetic material includes a NiFe alloy, the magnetic material may havea composition in which an iron content of the alloy is in a range of 10to 30 atomic %. An intensity of a magnetic field may be determinedaccording to the composition of the magnetic material. The iron contentin the composition of the magnetic material may affect coercive force.The iron content in the range of 10 to 30 atomic % is determined tocorrespond to the appropriate coercive force.

The seed layer 240 may include a resin or a metal. The uneven surface ofthe seed layer 240 may have a cross-section in which a plurality ofconcave portions and a plurality of convex portions are regularly orirregularly arranged. For example, the plurality of convex portions maybe arranged with a regular spacing therebetween, or may be arrangedsymmetrically with respect to the center of the seed layer 240.

Referring to FIG. 2B, a plan view of the magnetic sensor 200 of FIG. 2Ais illustrated. In this example, the protrusions 235 a have a shape of acircle in the plan view, and the uneven surface of the seed layer 240and the uneven surface of the IMC 250 also have the shape of a circle.However, in other examples, the uneven surface of the seed layer 240 mayhave a plan view in which a plurality of circles or a plurality ofpolygons are arranged in a loop shape. The plurality of circles may bearranged as to form concentric circles with respect to a center of theIMC 250. For example, an upper surface of an IMC 250 may includeelevations in the shape of two or more concentric circles. Further, inother examples, the IMC 250 may have a polygonal shape, rather than acircular shape.

Referring to FIG. 2B, the hall elements 210 has a plan view shape of across, and a center portion of the cross is aligned along an edge of theIMC 250. However, in other examples, the hall elements 210 may havevarious different shapes, such as a rectangular shape or a polygonalshape. Further, while six hall elements 210 are arranged along an edgeof the IMC 250 illustrated in FIG. 2B, in other examples, the number ofhall elements 210 may vary.

The IMC 250 formed on the seed layer 240 has an uneven surface with ageneral shape that corresponds to the uneven surface of the seed layer240. The stress affecting the hall element 210 may be reduced throughthe uneven surfaces of the IMC 250 and seed layer 240, as compared witha structure in which the IMC and seed layer have flat surfaces. An areaof the IMC 250 may be equal to or larger than that of the seed layer 240according to a fabrication method. Therefore, a magnitude of an offsetvoltage may be reduced and sensibility of the hall element 210 may beimproved.

FIGS. 3A to 3N are cross-sectional views illustrating an example of amethod of fabricating a magnetic sensor.

An example of a method of fabricating a magnetic sensor according toFIGS. 3A to 3N includes preparing a substrate 220 in which a pluralityof hall elements 210 are disposed; forming a protection layer 230 on thesubstrate 220; forming buffer layers 234 and 235 on the protection layer230; forming a plurality of protrusions 235 a on a surface of the bufferlayer 234 by etching the buffer layer 235; forming a seed layer 240having an uneven surface corresponding to the plurality of protrusions235 a on a surface of the protection layer 230; and forming an IMC 250having an uneven surface on the seed layer 240. The substrate 220 may bea semiconductor substrate. In an example, the substrate is asemiconductor substrate of a complementary metal-oxide semiconductor(CMOS). The IMC 250 may be formed of a magnetic material usingelectroplating. The IMC 250 may include an alloy containing two or morecomponents selected from the group consisting of Ni, Fe, Co, and Mn. Themagnetic material may have a coefficient of thermal expansion in a rangeof 5 to 20 ppm/° C. In an example in which the magnetic materialincludes a NiFe alloy, the Fe content of the magnetic material may be ina range of 10 to 30 atomic %. The seed layer 240 may include a resin anda metal. The cross-section of the uneven surface of the seed layer mayinclude a plurality of concave portions and a plurality of convexportions. The plurality of concave portions and the plurality of convexportions may be arranged regularly or irregularly. A pad 211 may beformed on a surface of one side of the substrate 220, as depicted inFIG. 3A.

An example of a method of fabricating the magnetic sensor will bedescribed in detail with reference to FIGS. 3A to 3N.

First, as illustrated in FIG. 3A, a hall element 210 and a pad 211 areformed on a semiconductor substrate 220. That is, a plurality of hallelements 210 are buried at intervals in the semiconductor substrate 220,or the plurality of hall elements 210 are formed at intervals on thesemiconductor substrate 220. The semiconductor substrate 220 may includea silicon (Si) substrate or a gallium arsenic (GaAs) substrate. The hallelements 210 may be formed by implanting P type ions or N type ions intothe semiconductor substrate 220. The hall elements 210 may have to sensechange in a magnetic force amplified by the magnetic material. Next, aprotection layer 231 is formed on the semiconductor substrate 220 inwhich the hall elements 210 are formed. The protection layer 231 mayinclude a silicon oxide layer and a silicon nitride layer.

Referring to FIG. 3B, a pattern 232 is used to perform an etchingprocess on the protection layer 231 to expose a pad 211. During theetching process, a portion of the protection layer 231 disposed abovethe pad 211 may be etched to expose the pad 211. The pattern 232 maycomprise a photoresist in a shape designed to expose the pad 211.

The pad 211 may be connected to a hall element 210 and may provide avoltage to the hall element 210. Several processes of forming aninsulating layer and a metal interconnection between the hall elements210 and the pad 211 may be performed. The metal interconnection may nothave to be deposited on the hall elements 210. It is because, when themetal interconnection is disposed on the hall elements 210, an intensityof a magnetic field amplified by an IMC 250 formed on the hall element210 is blocked by the interconnection and thus the intensity of themagnetic field affecting the hall element 210 may be reduced.

After the pad 211 is exposed, the pattern 232 is removed as illustratedin FIG. 3C. The pattern 232 may be removed through an ashing process.For example, a plasma ashing process may be used to remove the pattern232.

Referring to FIG. 3D, photosensitive polyimide (PSPI) is coated over theprotection layer 231 to obtain a first buffer layer 234 that covers theexposed pad 211 and the protection layer 231. The first buffer layer 234may include polyimide. Though the PSPI coating process, a top surface ofthe pad 211 may be covered with the first buffer layer 234.

As illustrated in FIG. 3E, the pad 211 is again exposed using a firstbuffer mask (not shown) disposed on the first buffer layer 234. That is,a portion of the first buffer layer 234 formed over the exposed portionof the pad 211 is removed through a PSPI exposure process. The firstbuffer layer 234 is easily removed through the exposure process.Thereafter, a curing process is performed to harden the remaining firstbuffer layer 234. The hardened first buffer layer 234 has a propertylike a thermal oxide layer and thus is not easily removed in asubsequent exposure and etching process.

Referring to FIG. 3F, a PSPI coating process is performed again to forma second buffer layer 235 on the hardened first buffer layer 234 and thepad 211. The second buffer layer 235 may include the same material asthe first buffer layer 234. For example, the second buffer layer 235 mayinclude polyimide. During the PSPI coating process, the top portion ofthe pad 211 is again covered with the second buffer layer 235.

Referring to FIG. 3G, a PSPI exposure process is performed on the secondbuffer layer 235 using a second buffer mask (not shown) disposed on thesecond buffer layer 235 to form a protrusion 235 a. While the protrusion235 a is formed, the top portion of the pad 211 that was covered by thesecond buffer layer 235 is again exposed. The second buffer 235 may beremoved from the first buffer 234 such that only the protrusions 235 aremain on the first buffer 234. After the protrusion 235 a is formed, acuring process is performed to harden the protrusion 235 a to form ahardened protrusion 235 a. A seed layer 240 and an IMC 250 to be formedsubsequent to the formation of the protrusion 235 a may not have a flatshape, but rather have a protruding shape due to the formation of theprotrusion 235 a thereunder.

Although one protrusion 235 a is depicted in FIG. 3G, a plurality ofprotrusion 235 a may be formed on the first buffer 234. In this example,the protrusion 235 a is used to form the uneven surface of an IMC 250.Referring to FIG. 3H, in order to form the seed layer 240 for the IMC250 that has an uneven surface, the protrusion 235 a may be formed tohave a rectangular shape in a cross-sectional view or may be formed tohave a shape having a positive slope, which a top thereof being narrowerthan a bottom thereof, in a cross-sectional view. That is, thecross-sectional view of the protrusion 235 a may have a taperedtrapezoid shape. An upper surface of the seed layer 240 formed thereonmay have a protrusion of a similar shape because, when a material forthe seed layer 240 such as TiW and Cu is deposited through a physicalvapor deposition (PVD) method or a sputtering method, the material forthe seed layer 240 may be formed so as to have to a uniform depositionthickness on a surface of the protrusion 235 a. On the contrary, whenthe protrusion 235 a has a shape having a negative slope in across-sectional view, the seed layer 240 may not be formed to have auniform deposition thickness. Therefore, in the example illustrated inFIG. 3H, the protrusion 235 a has a positive slope.

Referring to FIG. 3H, a TiW layer 242 and a Cu layer 241 arecontinuously deposited on the first buffer layer 234 on which theprotrusion 235 a is formed as the seed layer 240 for electroplating. TheTiW layer 242 and the Cu layer 241 may be formed through a sputteringmethod or a vacuum evaporation method. Therefore, in the exampledepicted in FIG. 3H, the Cu layer 241 is formed on the TiW layer 242. Atotal thickness of the TiW layer 242 and a Cu layer 241 may be in arange of 200 to 800 nm The seed layer 240 serves to perform anelectroplating process on the magnetic material well in a subsequentprocess. As described above, because the seed layer 240 is formed on theprotrusion 235 a as to cover the protrusion 235 a, the seed layer 240has an uneven surface in a cross-sectional view.

Referring to FIG. 3I, a pattern mask 243 for forming the IMC 250 isfirst formed through photolithography. The IMC 250 may include amagnetic material. Hereinafter, the magnetic material from which the IMC250 is formed is referred to as the magnetic material 250.

As illustrated in FIG. 3J, a NiFe alloy is deposited on the seed layer240 through electroplating using the pattern mask 243. The NiFe alloyforms the magnetic material 250. The magnetic material 250 deposited onthe seed layer 240 may have an uneven surface that corresponds to theprotrusion 235 a.

Referring to FIG. 3K, after the electroplating is completed, the patternmask 243 is removed and only the magnetic material 250 remains on theseed layer 240.

Referring to FIG. 3L, the seed layer 240 including the Cu layer 241 andthe TiW layer 242 disposed on the pad 211 is removed through a wetetching process. As a result, the seed layer 240 remains only below themagnetic material 250, and the remaining portion of the seed layer 240is removed as to expose the first buffer 234 and the pad 211. Themagnetic material 250 is formed on the hardened protrusion 235 a. Thus,the magnetic material 250 is formed with an uneven upper surface. Due tothe uneven surface of the magnetic material 250, stress imposed on thesubstrate 220 may be reduced and an offset voltage may be reduced.

Referring to FIG. 3M, a third buffer layer 251 is formed on the seedlayer 240 so as to cover the magnetic material 250 through a PSPIcoating process. In this example, the third buffer layer 251 may includepolyimide.

Referring to FIG. 3N, a PSPI exposure and curing process is formed onthe third buffer layer 251 using a third buffer mask (not shown)disposed on the third buffer later 251 to exposure a top portion of thepad 211. The example of the magnetic sensor 200 is completed with thecuring process.

FIGS. 4A to 4O are cross-sectional views illustrating another example ofa method of fabricating a magnetic sensor.

Referring to FIGS. 4A to 4O, various steps performed in the example of afabrication method of a magnetic sensor illustrated are substantiallythe same as those performed in the example of fabrication method asillustrated in FIGS. 3A to 3N. Thus, detailed description thereof willbe omitted.

For example, the steps performed in FIGS. 4A and 4B are substantiallythe same as the steps performed in FIGS. 3A and 3B, and the detaileddescription thereof will be omitted. The example of the method offabricating a magnetic sensor according FIGS. 4A to 4O, however, furtherinclude forming a corrosion barrier layer to prevent a pad from beingcorroded. Referring to FIG. 4C, a pad 211 is provided on a surface of asemiconductor substrate 220 on one side thereof, and then an insulatinglayer is further deposited on the pad 211 and protection layer 231 toform a corrosion barrier layer 231 a. In this example, the corrosionbarrier layer 231 a may include an oxide-based or nitride-basedinsulating layer and may be deposited through a plasma-enhanced chemicalvapor deposition (PECVD) method. When the corrosion barrier layer 231 ais formed through a PECVD method, the corrosion barrier layer 231 a mayinclude a silicon oxide layer using a tetra ethyl ortho silicate (TEOS)material. For this example, the thickness of the corrosion barrier layer231 a may be in a range of 5 to 50 nm The thickness may be 40 nm or lessbecause it may be difficult to etch the insulating layer for thecorrosion barrier layer to expose the pad 211 when the thickness of thecorrosion barrier layer is more than 50 nm. On the other hand, when theinsulating layer has a thickness of less than 5 nm, the insulating layermay be too is very thin and may not serve as a protection layer. Thenumerical limit values for the thickness are the desirable valueobtained using resultant values obtained through repeated experiments,and may be associated with certain characteristics and effects for themanufactured magnetic sensor 200.

Referring to FIG. 4D, a first buffer layer 234 is deposited on thecorrosion barrier layer 231 a through a PSPI coating process. Thecorrosion barrier layer 231 a is disposed between the protection layer231 and the first buffer layer 234. Referring to FIGS. 4E and 4G,repeated PSPI exposure and developing processes are performed on thefirst buffer layer 234 and a second buffer layer 235. During the PSPIexposure and developing processes, the top surface of the pad 211 iscovered with the corrosion barrier layer 231 a. Thus, the top of the pad211 may be prevented to be corroded from a tetra methyl ammoniumhydroxide (TMAH) solution that is one of developing solutions used inthe PSPI exposure and developing processes of the first and secondbuffer layers.

Referring to FIG. 4H, a seed layer 240 including a Cu layer 241 and aTiW layer 242 is formed on the corrosion barrier layer 231 a and thefirst buffer layer 234 having formed thereon a protrusion 235 a.

Referring to FIGS. 4I-4K, a magnetic material 250 is formed on the seedlayer 240 in processes substantially similar to FIG. 3I-3K.

Referring to FIG. 4L, a portion of the seed layer 240 is removed throughetching. As illustrated in FIG. 4L, because the corrosion barrier layer231 a is formed on the pad 211, the pad is prevented from being etchedeven when the seed layer 240 is etched. Referring to FIG. 4N, after thethird buffer layer 251 is formed in FIG. 4M, because the top portion ofthe pad 211 is protected by the corrosion barrier layer 231 a, thecorrosion of the pad 211 may be prevented during the exposure anddeveloping processes of the third buffer layer 251.

Referring to FIG. 4O, the corrosion barrier layer 231 a that is formedas described above is removed after the PSPI exposure and the curingprocess is performed on the third buffer layer 251 using a third buffermask (not shown) disposed on the third buffer layer 251. Therefore, thetop portion of the pad 211 is finally opened through a process ofremoving the corrosion barrier layer 231 a.

Thus, referring to the example illustrated in FIGS. 4A-4O, the topportion of the pad 211 may be protected from corrosion caused by a TMAHsolution that is used as one of developing solutions during the repeatedPSPI exposure and developing processes. The corrosion barrier layer 231a is removed from the top of the pad after the repeated PSPI exposureand developing processes are performed. The corrosion barrier layer 231a may preferably include a material such as a silicon oxide layer thatcan be chemically endured from a solution such as a TMAH solution. Whenthe top of the pad is corroded, an electrical contact failure may becaused; thus, the prevention of the corrosion is desirable.

FIG. 5 illustrates scanning electron microscope (SEM) photographs for aperspective view from the top and a cross-sectional view of the unevensurface of an IMC 250 of the magnetic sensor 200 fabricated according tothe above-described examples.

The SEM photograph (A) of FIG. 5 depicts a perspective view from the topof the uneven surface of the IMC 250, and the SEM photograph (B) of FIG.5 depicts a cross-sectional view of the IMC 250 having the unevensurface through a protrusion 235 a formed on the first buffer layer 234as a magnified view of the SEM photograph (A). As illustrated in the SEMphotograph (A), the example of magnetic sensor includes protrusions inthe shape of two concentric circles, which form corresponding unevennesson the upper surface of the IMC 250.

FIGS. 6A and 6B are graphs showing stress in an X-axis direction and aY-axis direction affecting a hall element, and FIGS. 7A and 7B aregraphs showing a simulation result of a magnetic flux of the IMC.

As described above, the hall element 210 configured to sense a magneticfield is disposed below the IMC 250, and the protrusion 235 a reduces orminimizes the stress affecting characteristics of the magnetic sensor200 around the hall element 210. In general, most of the stress isapplied to edge portions B of the IMC 250. It can be seen from thesimulation that the stress affects the hall element 210 and the resultis illustrated in FIGS. 6A and 6B.

For instance, FIG. 6A shows the stress in the X-axis direction of theIMC according to a depth of a hall element, and FIG. 6B shows the stressin the Y-axis direction of the IMC 250. Here, the stress refers topressure or compressive stress or tensile stress affecting the substratein which the hall element is formed. Multi-layered insulating layers areinterposed between the IMC and the hall element. The stress is appliedto the insulating layers according to the shape of the IMC and thestress is transferred to the hall element again through the insulatinglayers. According to an example of the present disclosure, because theIMC has a thin thickness of 5 to 20 μm and a very large width of 200 to400 μm, the stress may largely affect the insulating layers and the hallelements disposed below the IMC.

It can be seen from FIGS. 6A and 6B that the IMC having the unevensurface has the lowest stress in the X-axis direction and the Y-axisdirection indicated by “C” as compared with the IMCs having a flatsurface in the related art indicated by “A” and “B”. The offsetcharacteristic may be improved and sensibility may be increased throughthe improved stress effect. A plurality of uneven shapes is moreeffective in improving the stress than one uneven shape. For example, asdescribed in FIG. 2A, the uneven shape of the IMC 250 may be formed byelectroplating a magnetic material for the IMC on the protrusion 235 ahaving a width of 5 to 30 μm and a height of 1 to 10 μm and the seedlayer 240 as described in FIG. 2A.

In order to check whether the IMC 250 having the uneven surface that isdescribed above to improve the stress performs a function of verticallyconcentrating a magnetic field, a simulation was performed with amagnetic field.

FIGS. 7A and 7B illustrate a simulation result of a magnetic flux. Itcan be seen that a value (Bz shown in FIG. 7B) of a vertical componentof the magnetic field in which the IMC having the uneven surface issimilar to a value (Bz shown in FIG. 7A) of a vertical component of themagnetic field in which the IMC having the flat surface in the relatedart affects the hall element.

Various examples of magnetic sensors and methods of fabricating the sameare described above. According to an example, a fabrication process ofproducing an IMC having an uneven shape and improved sensorcharacteristics is described. The IMC may exhibit improved sensorcharacteristics due to a uniform reduction in stress of the hallelements.

In an example, a magnetic sensor includes: a semiconductor substrate inwhich a plurality of hall elements are disposed; a protection layerformed on a semiconductor substrate; a seed layer formed on theprotection layer; and an integrated magnetic concentrator (IMC) formedon the seed layer. Each of the seed layer and the IMC may have an unevensurface. An area of the IMC may be equal to or larger than that of theseed layer.

The protection layer may include a plurality of protrusions (orelevations) formed on a surface thereof. Each of the uneven surfaces ofthe seed layer and the IMC may have a cross-section in which a pluralityof concave portions and plurality of convex portions are regularly orirregularly arranged. The hall elements may be disposed so as to overlapedge portions of the IMC in a vertical direction of the magnetic sensor.The protection layer may include a passivation insulating layer and abuffer layer, and the protection layer may further include a corrosionbarrier layer.

The corrosion barrier layer may include any one of a silicon oxide layerand a silicon nitride layer. The corrosion barrier layer may have athickness of 5 to 50 nm. The corrosion barrier layer may be interposedbetween the passivation insulating layer and the buffer layer and theprotrusions may include polyimide.

When the IMC includes a nickel-iron (NiFe) alloy, the IMC may have acomposition in which a content of Fe is 10 to 30 atomic %.

The seed layer may include a titanium tungsten (TiW) material and acopper (Cu) material.

In an example, a method of fabricating a magnetic sensor includes:preparing a substrate in which a plurality of hall elements aredisposed; forming a protection layer on the substrate; forming a bufferlayer on the protection layer; forming a plurality of protrusions on asurface of the buffer layer; forming a seed layer having an unevensurface corresponding to the plurality of protrusions; and forming anintegrated magnetic concentrator (IMC) having an uneven surface on theseed layer. The uneven surface of the seed layer or the IMC may have across-section in which a plurality of concave portions and a pluralityof convex portions are regularly or irregularly arranged.

The seed layer may include double layers of a titanium tungsten (TiW)material and a copper (Cu) material. The method may further includeforming a corrosion barrier layer.

The corrosion barrier layer may include any one of a silicon oxide layerand a silicon nitride layer. The corrosion barrier layer may be formedbetween the protection layer and the buffer layer. The protrusions mayinclude polyimide.

In an example of fabricating a magnetic sensor having theabove-described configuration, the fabrication process may be simplifiedby forming an IMC having an uneven surface without using an accurateetching process for horizontally etching the seed layer. Further, thestress of the hall element may be reduced to constant uniformity andsensor characteristics may be improved through formation of theregularly uneven shape of the IMC.

The foregoing examples are provided for illustrative purposes, and arenot to be construed as limiting the present disclosure. The drawings maynot be necessarily to scale, and, in some instances, proportions mayhave been exaggerated in order to clearly illustrate features of theexamples. When a first layer is referred to as being “on” a second layeror “on” a substrate, it may not only refer to a case where the firstlayer is formed directly on the second layer or the substrate but mayalso refer to a case where a third layer exists between the first layerand the second layer or the substrate.

In the claims, means-plus-function clauses are intended to cover thestructures described herein as performing the recited function, and notonly structural equivalents but also equivalent structures.

A number of examples have been described above. Nevertheless, it will beunderstood that various modifications may be made. For example, suitableresults may be achieved if the described techniques are performed in adifferent order and/or if components in a described system,architecture, device, or circuit are combined in a different mannerand/or replaced or supplemented by other components or theirequivalents. Accordingly, other implementations are within the scope ofthe following claims.

What is claimed is:
 1. A method of fabricating a magnetic sensor, themethod comprising: forming hall elements; forming a protection layercomprising a thin portion having a first thickness and comprising athick portion having a second thickness that forms a protrusion thatprotrudes upward from an upper surface of the protection layer; forminga seed layer disposed above the hall elements; and forming an integratedmagnetic concentrator (IMC) disposed above the hall elements and theseed layer, the IMC comprising an elevated portion protruding upwardfrom an upper surface of the IMC, and the elevated portion overlappingwith the protrusion of the protection layer.
 2. The method of claim 1,wherein the seed layer or the IMC has a cross-section in which concaveportions and convex portions are arranged.
 3. The method of claim 1,wherein the seed layer comprises a titanium tungsten (TiW) layer and acopper (Cu) layer.
 4. The method of claim 1, wherein the protectionlayer comprises a corrosion barrier layer.
 5. The method of claim 4,wherein the corrosion barrier layer comprises a silicon oxide layer or asilicon nitride layer.
 6. The method of claim 1, wherein the protrusioncomprises polyimide.
 7. The method of claim 1, wherein the protrusion isin contact with the seed layer.
 8. The method of claim 1, wherein theprotrusion is formed to generate an uneven surface of the IMC and reduceincident stress on at least one hall element.
 9. A method of fabricatinga magnetic sensor, the method comprising: a protection layer above asubstrate in which hall elements are disposed; forming a buffer layerabove the protection layer comprising thin portions having firstthicknesses and comprising thick portions having second thicknesses thatare thicker than the thin portions that form protrusions above a topsurface of the buffer layer; forming a seed layer having an unevensurface corresponding to the protrusions with an elevated portion thatprotrudes from an upper surface of the seed layer in a substantiallynormal direction to an upper surface of the substrate; and forming anintegrated magnetic concentrator (IMC) having an uneven surface abovethe seed layer and comprising an elevated portion that protrudes from anupper surface of the IMC in the direction substantially normal to theupper surface of the substrate.
 10. The method of claim 9, wherein theuneven surface of the seed layer or the uneven surface of the IMC has across-section in which concave portions and convex portions arearranged.
 11. The method of claim 9, wherein the seed layer comprises atitanium tungsten (TiW) layer and a copper (Cu) layer.
 12. The method ofclaim 9, wherein the protection layer comprises a corrosion barrierlayer.
 13. The method of claim 12, wherein the corrosion barrier layercomprises a silicon oxide layer or a silicon nitride layer.
 14. Themethod of claim 9, wherein the protrusions comprise polyimide.
 15. Amethod of fabricating a magnetic sensor, the method comprising: forminghall elements; forming a seed layer disposed above the hall elements;and forming an integrated magnetic concentrator (IMC) disposed above thehall elements, the IMC comprising an elevated portion protruding upwardfrom an upper surface of the IMC, wherein the hall elements are disposedsuch that a peripheral edge of the IMC overlaps with a width of the hallelements, and wherein the seed layer overlaps the hall elements.
 16. Themethod of claim 15, wherein the elevated portion of the IMC has a shapeof a ring or concentric rings.
 17. The method of claim 15, wherein aperipheral edge of the seed layer overlaps the width of the hallelements.
 18. The method of claim 1, wherein the hall elements comprisea first hall element and a second hall element, and wherein theprotrusion of the protection layer is disposed to overlap an areabetween the first hall element and the second hall element.
 19. Themethod of claim 1, wherein forming the protection layer comprises:forming a first buffer layer disposed above the hall elements; andforming a second buffer layer disposed above the first buffer layer,wherein the second buffer layer comprises the protrusion of theprotection layer.
 20. The method of claim 9, wherein the hall elementscomprise a first hall element and a second hall element, and wherein atleast one of the protrusions is disposed to overlap an area between thefirst hall element and the second hall element.
 21. The method of claim15, further comprising: forming a protection layer comprising a thinportion having a first thickness and comprising a thick portion having asecond thickness that forms a protrusion that protrudes upward from anupper surface of the protection layer.
 22. The method of claim 15,wherein the hall elements comprise a first hall element and a secondhall element, and wherein the elevated portion of the IMC is disposed tooverlap an area between the first hall element and the second hallelement.